use strict;
my %fnames; # use a hash to eliminate duplicates
while (<DATA>) {
   if (/^(\w+_\d+)_\d+\w+/) {
       $fnames{$1} = 1;
   }
}
foreach (keys %fnames) {
   print "$_\n";
}

__DATA__
smith_13_503_de7.p
smith_13_502_de7.v
jones_104_503_de7.p
jones_104_502_de7.v